I think you've got some good answers here but I will put in my two cents.

I don't feed frozen food for now and freeze dried is definitely just a treat. Both have a slight risk of internal parasites (which I have dealt with and they are a pain to treat) but frozen is a bit higher. The freeze drying process usually eliminates that risk. With frozen food you have to be careful not to let any unused portions thaw. One reason I don't have frozen food is that the closest place to me that sells it is an hour away and I'm afraid of it thawing out on the drive home and too lazy to pack a cooler full of ice, lol. Plus I don't want to waste an hour trip just to get food and come right back.

There is also really no evidence that freeze dried foods cause constipation or bloat and soaking them is not a good idea because they do contain some nutrients and soaking them before feeding causes them to lose those nutrients. To put this into perspective, I feed my CT who has chronic bloat issues freeze dried food that is not Pre soaked and it doesn't cause any more bloating than pellets, if not less bloating than pellets.

I feed a variety of pellets, which should still be your staple. My main two are New Life Spectrum and Omega One. New Life Spectrums small size allows smaller fish to be able to eat them with ease but means you have to feed more of them (6 per day). Omega One is a little larger and only need to be fed 3 per day. New Life Spectrum, IMO, is good because it does not soak and expand and then deteriorate if it sinks like other pellets do, but it is also not good for soaking in medication if you ever need to do so.

I'm not sure what size the top fin pellets are but I would assume 6 is a little much for MOST bettas, but not all. You will find that different bettas need different amounts of food. For instance, my CT is also blind and not very active and if I fed him the same amount I feed my other fish he would get very, very bloated. Its kind of a guessing game with him and he usually gets more than 1 fast day per week because of it. I feed my sorority tank a little more because they are very active and I want to make sure all the girls get some.

Top-Fin pellets are a little on the bigger side. I crush them a bit so he can eat them easily, so he probably gets more like 5 since I don't throw the really powdery bits in. I do plan to have a fasting day for him.

My last betta had bloat once (and he didn't even eat as much) so I know what to look for. He's just so active and seems hungry all the time...

If you make sure frozen foods don't thaw until feeding, is there still a risk of parasites? How do worms even carry parasites?..

Most of them seem hungry all the time ;) the more active they are and the bigger they are, the more they can eat. But technically, under-feeding is usually better than over-feeding. If the feeding schedule works fine for him, I wouldn't worry. I might look for a better quality food though. I believe top fin isn't that great but I don't know the ingredients so I'd look at the ingredients if I were you.

The risk of parasites is very small. I'm not sure exactly how it works. If you do notice long white stringy poo ever, I'd throw out the whole batch of frozen food. This is uncommon. My fish's parasites did not come from frozen foods. I'm actually still not sure where they came from.

To be honest, I never see him poo.(I know he does though) He probably burns it off before it's out of his body...
Top-Fin has decent protein, but fish meal is the first ingredient.
How many frozen blood worms should I feed him at once?

Lol when you first see him poo it'll be interesting xD but generally you just look to see if its the same color as the food you feed them. Sometimes you can see it at the bottom of the tank but with internal parasites, it can be a clear ish white color and hard to see in the rocks. Eventually you will see him in the act. Just take quick glances at him throughout the day. Internal parasites may also cause uncontrollable floating which you would not miss if you saw it.

I don't use hammocks but they are great and most fish love them. But if there is a metal wire in it, it needs to be removed first because it can rust and release toxins. I know some people who have made their own hammocks out of craft mesh. They like places to rest near the surface. You should have several things for him to rest on by the surface, be it hammocks or floating logs or tall broad leafed silk or live plants

What size is the tank? I have several types and sizes of gravel vacs but my favorite is a mini vac from earl may. Its very simple, was only $6, and isn't too big for my tanks. The "regular" sized one at Walmart is huge for all my tanks and the biggest tank I have is a ten gallon.